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Percy Lazon De La Jara, Sho Takatori, Klaus Ehrmann, Arthur Ho, Brien Holden, Clayton Radke; Corneal Uptake of Oxygen In Vivo During Soft Contact Lens Wear. Invest. Ophthalmol. Vis. Sci. 2013;54(15):505. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Critical oxygen need of the human cornea during soft contact lens (SCL) wear has received decades of attention with polarograpy the primary in-vivo experiment. Unfortunately, classical analysis of the polarographic oxygen sensor (POS) misinterprets electrode behavior. We develop a new method to assess in-situ corneal oxygen uptake during SCL wear using a micro-polarographic Clark electrode.
After steady SCL wear and subsequent lens removal, a membrane-covered POS is immediately placed onto the cornea and transient oxygen tension recorded. A semi-logarithmic graph of oxygen tension versus time at long time is created to give corneal oxygen uptake, Jo(0). We apply our procedure to polarographic data for ten human subjects with 12 different commercial SCL during open eye.
The average corneal oxygen uptake rates for ten subjects with 12 different commercial SCLs vary from 2 - 10 μL(STP)/cm2 /h at open eye. In Fig. 1, filled circles give oxygen uptake into the cornea with lens wear, Jo(0), relative to that without lens wear, Jo*(0), as a function of SCL transmissibility. The solid line corresponds to a theoretical model, which corroborates well with the experimental data. Lenses with oxygen transmissibilities around Dk/t ~ 150 hBarrer/cm have uptake rates of ~ 10 μL(STP)/cm2/h, in close agreement with our previously obtained no-lens human uptake rates of 9 - 13 μL(STP)/cm2/h at open eye (Takatori et al. IOVS. 2012; 53: 6331-6337).
Application of the classical procedure to our experimental data gives corneal-uptake results that are about three to five times smaller those classically reported. According to our corrected procedure, full oxygenation of the human eye, 11.3 μL/cm2 /h for the 10 subjects studied, is reached only asymptotically (see Fig. 1). That is, very high lens transmissibility is required before the lens no longer impedes oxygen transport. Conversely, 95 % anterior corneal oxygenation is achieved with a lens transmissibility of 150 hBarrer/cm.
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